Memory devices are common in electronic systems and computers to store data. These memory devices may be volatile memory, where the stored data is lost if the power source is disconnected or removed, or non-volatile, where the stored data is retained even during power interruption. An example of a non-volatile memory device is the programmable metallization cell (PMC) also known as conductive bridging RAM (CBRAM), nanobridge memory, or electrolyte memory.
A PMC utilizes an ion conductor or solid electrolyte such as a chalcogenide type or an oxide type and at least two electrodes (e.g., an anode and a cathode) with the ion conductor or solid electrolyte between the electrodes. When a voltage is applied across the electrodes, conducting filaments rapidly grow from the cathode through the ion conductor or solid electrolyte towards the anode. This gives rise to a low resistance state. When an electric field of opposite polarity is applied across the electrodes, the conducting filaments dissolve and the conducing paths are disrupted. This gives rise to the high resistance state. The two resistance states that are switchable by the application of the appropriate electric field are used to store the memory data bit of “1” or “0”.
Although the conducting filaments provide an accurate path for current flow from one electrode to the other, the creation and dissolution of the conducting filaments can be unpredictable. The conductive paths are generated and dissolved at random locations when the electric potential of a proper value, and polarity, is applied. Thus, the position and occurrence of the filaments is not accurate or reproducible. These factors lead to variation in cell behavior, especially as the cell sized is scaled down for high packing densities. Therefore, improvements are needed in PMC to reduce individual cell behavior variability.